The present invention relates to a stack, especially to a structure of fuel cell assembly.
There are limited resources on the earth. Under the condition that the population density keeps increasing, the resources available for the individual are decreasing dramatically day after day. Moreover, fast development of industries as well as overexploitation of resources leads to over-consumption of energy. The earth is getting worse for people to live on. Thus besides higher efficiency, energy technology further got to have advantage of low pollution. The fuel cell technology is becoming increasingly popular in power generation technology that matches these requirements.
Refer to FIG. 1 & FIG. 2, respectively are explosive view and perspective view of a stacked fuel cell set disclosed in Taiwanese patent No. 237920. As shown in figure, a conventional fuel cell includes a plate for flow fields 10, two fuel cell units 20 and a locking member. The two fuel cell units 20 are disposed on two sides of the plate for liquid channels 10. The plate for liquid channels 10 consists of a fuel inlet 11 and a flow field 13, connecting with each other for drawing liquid fuel. The locking member is composed of a first part 32, a second part 34 and a plurality of openings 36, respectively arranged outside the two fuel cell units 20 so that the fuel cell units 20 contact and reacts with air from outside through the openings 36 for generating electricity.
Refer to FIG. 3, the fuel cell unit 20 is a proton exchange membrane fuel cell that includes a netty metal plate 22 and a membrane electrode assembly 24.
The netty metal plate 22 is made by drawing of metal sheet or knitted metal mesh and having a first netty area 222 and a second netty area 224. The membrane electrode assembly 24 is disposed on the second netty area 224. The membrane electrode assembly 24 consists of an anode catalyst layer 242, a proton exchange membrane 244 and a cathode catalyst layer 246. The anode catalyst layer 242 and the cathode catalyst layer 246 are respectively arranged on two sides of the proton exchange membrane 244. The anode catalyst layer 242 is arranged on the second netty area 224.
In order to make the fuel cell work, the fuel is intake through the inlet 11 and the fuel cell unit 20 is a proton exchange membrane fuel cell. The fuel can be aqueous methanol solution made by water mixed with methyl alcohol. When the aqueous methanol solution is filled into the flow field 13 through the fuel inlet 11, it's oxidized at the anode catalyst layer 242 to generate positive hydrogen ions negative electrons and carbon dioxide. The hydrogen ions are transferred through the proton exchange membrane with high ionic conductivity and the high selective permeability to the cathode catalyst layer 246 while electrons are transferred through metal plate 22 of the fuel cell unit 20, loadings of the fuel cell unit 20 and then to the cathode catalyst layer 246. At the cathode catalyst layer 246, the hydrogen ions from the anode combine with the electrons and oxygen from air to produce water.
Water is mostly a problem on the cathode side of the fuel cell because it blocks reaction area of the fuel cell. Thus the hydrogen ions and the electrons at the cathode catalyst layer 246 can't react with oxygen in the air. Therefore, efficiency of reaction area of the fuel cell is reduced. A cooling fan is used to accelerate vaporization of water as well as velocity of air flow so that the cathode catalyst layer 246 contacts with more oxygen and further efficiency of the reaction area is improved. But such way still can't make water volatilize quickly. Thus water may still form a barrier at the cathode catalyst layer 246.
Thus the present invention provides a structure of fuel cell assembly that discharges water quickly so as to avoid reduced performance caused by water accumulation. Moreover, fuel is distributed more uniformly over reaction area of the fuel cell to overcome above shortcomings.